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Error while trying to add a button using JavaFX

I have a problem while trying to add a button on an HBox. The error that I got is "Cannot invoke "javafx.scene.layout.HBox.getChildren()" because "this.buttonBox" is null" even though I already have an HBox with fx:id buttonBox. Can someone help me with this?
And I also tried to add a new HBox on the code and then add a button but the button did not show up.
Here is my code:
package com.example.simplemaps;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.geometry.Insets;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.layout.HBox;
import java.io.IOException;
import java.util.ArrayList;
public class View {
public static final String INTERFACE_LOCATION = "maps-view.fxml";
private static final Image IMG_BACKGROUND = new Image("com/example/simplemaps/AisleForward.jpg");
private static final Image IMG_FOREGROUND = new Image("com/example/simplemaps/Bunny.png");
//private Controller controller;
#FXML private Label label;
#FXML private ImageView imageBackground;
#FXML private ImageView imageForeground;
#FXML private HBox buttonBox;
public View() {
//controller = new Controller();
}
public void pickUp()
{
// TO DO
}
public void putDown()
{
imageForeground.setImage(IMG_FOREGROUND);
}
public void start()
{
try
{
FXMLLoader fxmlLoader = new FXMLLoader(SimpleMaps.class.getResource(INTERFACE_LOCATION));
Parent anchorPane = fxmlLoader.load();
SimpleMaps.mainStage.setScene(new Scene(anchorPane));
SimpleMaps.mainStage.show();
}
catch(IOException e)
{
e.printStackTrace();
System.exit(1);
}
}
public void addWhereToButtons(String exit) {
//for(String exit : exits) {
Button button = new Button(exit);
HBox.setMargin(button, new Insets(10.0,0.0,10.0,5.0));
buttonBox.getChildren().add(button);
button.setOnAction(new EventHandler<ActionEvent>() {
#Override public void handle(ActionEvent e) {
//controller.selectExitDirection(exit);
}
}
);
//}
}
}
This is the error:
/Library/Java/JavaVirtualMachines/openjdk.jdk/Contents/Home/bin/java --module-path /Users/ulfianidian/Desktop/IPPO/javafx-sdk-17.0.0.1/lib --add-modules javafx.controls,javafx.fxml -Djava.library.path=/Users/ulfianidian/Desktop/IPPO/javafx-sdk-17.0.0.1/lib -javaagent:/Applications/IntelliJ IDEA CE.app/Contents/lib/idea_rt.jar=51875:/Applications/IntelliJ IDEA CE.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Users/ulfianidian/Desktop/IPPO/SimpleMaps/target/classes:/Users/ulfianidian/Desktop/IPPO/javafx-sdk-17.0.0.1/lib/javafx-swt.jar:/Users/ulfianidian/Desktop/IPPO/javafx-sdk-17.0.0.1/lib/javafx.web.jar:/Users/ulfianidian/Desktop/IPPO/javafx-sdk-17.0.0.1/lib/javafx.base.jar:/Users/ulfianidian/Desktop/IPPO/javafx-sdk-17.0.0.1/lib/javafx.fxml.jar:/Users/ulfianidian/Desktop/IPPO/javafx-sdk-17.0.0.1/lib/javafx.media.jar:/Users/ulfianidian/Desktop/IPPO/javafx-sdk-17.0.0.1/lib/javafx.swing.jar:/Users/ulfianidian/Desktop/IPPO/javafx-sdk-17.0.0.1/lib/javafx.controls.jar:/Users/ulfianidian/Desktop/IPPO/javafx-sdk-17.0.0.1/lib/javafx.graphics.jar com.example.simplemaps.SimpleMaps
Exception in Application start method
java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:465)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:364)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1071)
Caused by: java.lang.RuntimeException: Exception in Application start method
at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:901)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:196)
at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.NullPointerException: Cannot invoke "javafx.scene.layout.HBox.getChildren()" because "this.buttonBox" is null
at com.example.simplemaps.View.addWhereToButtons(View.java:66)
at com.example.simplemaps.Controller.start(Controller.java:21)
at com.example.simplemaps.SimpleMaps.start(SimpleMaps.java:20)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:847)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
Exception running application com.example.simplemaps.SimpleMaps
Process finished with exit code 1

You need to cast a new HBox to buttonBox, as such.
HBox buttonBox = new HBox();

LinkedList erased in Action Handelers methods in JavaFX

I am working on an App that simulates an online shop for my Data Structures course, I am currently using JavaFX in the Eclipse IDE and Scene Builder for the GUI design, however I am trying to use a Double LinkedList to store the Accounts in the Sign In UI window, but for some reason every time that I try to insert a new Account object (in the Action Event method) into my List it doesn't inserts it, at least if I try to print it´s toString gives me a Null pointer Exception, but if the insert and the println is in the start method works. Last year a did an MP3 player using JavaFX but in Netbeans and I didn't use Scene Builder and the List did work, some one has any idea why is this happening?
package com.javafx.quvbi.controller;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.stage.Stage;
import javafx.scene.input.MouseEvent;
import java.io.IOException;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
public class interfazController extends Application {
#FXML
private Button pausa, CreateAccBttn, LoginBttn;
#FXML
private TextField NameTF, AccountTF, PasswordTF, CardTF;
//Data
ListaDobleEnlazada<Account> accList;
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) throws Exception {
// TODO Auto-generated method stub
//NameTF = new TextField();
//AccountTF = new TextField();
//PasswordTF= new TextField();
//CardTF = new TextField();
accList = new ListaDobleEnlazada<Account>();
//accList.insertarInicio(new Account("Diego","Qubi","22f24rf2",123321));
Parent root = FXMLLoader.load(getClass().getResource("/view/OptionUI.fxml"));
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
System.out.println(accList.toString());
}
public ListaDobleEnlazada<Account> getAccounts() {
return accList;
}
#FXML
public void controlMusica(ActionEvent event) {
System.out.println("musica");
System.out.println(getAccounts().getInicio().toString());
}
public void CreateAccClick(MouseEvent event) throws IOException {
if(!NameTF.getText().isEmpty() && !AccountTF.getText().isEmpty() && !PasswordTF.getText().isEmpty() && !CardTF.getText().isEmpty()) {
accList.insertarInicio(new Account(NameTF.getText(), AccountTF.getText(), PasswordTF.getText(), Integer.parseInt(CardTF.getText())));
}
}
#SuppressWarnings("restriction")
public void createAccount(ActionEvent event) throws IOException {
if(!NameTF.getText().isEmpty() && !AccountTF.getText().isEmpty() && !PasswordTF.getText().isEmpty() && !CardTF.getText().isEmpty()) {
Parent loginUI = FXMLLoader.load(getClass().getResource("/view/GUI2.fxml"));
Scene logInScene = new Scene(loginUI);
Stage window = (Stage)((Node)event.getSource()).getScene().getWindow();
window.setScene(logInScene);
window.show();
System.out.println(NameTF.getText());
System.out.println(AccountTF.getText());
System.out.println(PasswordTF.getText());
System.out.println(CardTF.getText());
//this.accList.insertarInicio(new Account(NameTF.getText(), AccountTF.getText(), PasswordTF.getText(), Integer.parseInt(CardTF.getText())));
}
}
public void loginAccount(ActionEvent event) throws IOException {
Parent loginUI = FXMLLoader.load(getClass().getResource("/view/GUI2.fxml"));
Scene logInScene = new Scene(loginUI);
Stage window = (Stage)((Node)event.getSource()).getScene().getWindow();
window.setScene(logInScene);
window.show();
}
}

How to open the another FXML file on action of button click? [duplicate]

i have seen other answers but nothing have helped me
(sorry new to GUI only know basics of swing)
this is main class
package application;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
try {
Parent root=FXMLLoader.load(getClass().getClassLoader().getResource("/Main.fxml"));
Scene scene = new Scene(root,400,400);
scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
primaryStage.setScene(scene);
primaryStage.show();
}
catch(Exception e) {
e.printStackTrace();
System.exit(0);
}
}
public static void main(String[] args) {
launch(args);
}
}
this is another class whose method i want to invoke
package application;
import java.util.Random;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Label;
public class MainController {
#FXML
private Label myMessage;
void generaterandom (ActionEvent event){
Random rand=new Random();
int myrand=rand.nextInt(50)+1;
myMessage.setText(Integer.toString(myrand));
System.out.println(Integer.toString(myrand));
}
}
i will add xml file if needed .
this is the error i am getting
java.lang.NullPointerException: Location is required.
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3207)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
at application.Main.start(Main.java:14)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl .java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:32 6)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)

getClass().getClassLoader().getResource(...) will load a resource from a path relative to the classpath. Since you placed the FXML file in the application pacakge, you need:
Parent root=FXMLLoader.load(getClass().getClassLoader().getResource("application/Main.fxml"));
If you just use getClass().getResource(...), and do not prefix the path with /, it will load from a path relative to the current class. So
Parent root=FXMLLoader.load(getClass().getResource("Main.fxml"));
should also work.
Make sure that your FXML file is being exported to the build folder, along with the .class files.

try{
scene.getStylesheets().add(new File(pathTocssFile).toURI().toURL().toExternalForm());
} catch (MalformedURLException e) {
e.printStackTrace();}

Java Runtime Exception. Java FX

I have tried to learn Java FX so I used some of the Oracle Eample Code but when I tried to run it in Netbean IDE, It gives me a Runtime Error. Here is a Piece of code :
public class WebViewTestOne {
private Scene scene;
#Override
public void start(Stage stage) {
stage.setTitle("Web View");
scene = new Scene(new Browser(),750,500, Color.web("#666970"));
stage.setScene(scene);
scene.getStylesheets().add("webviewsample/BrowserToolbar.css");
stage.show();
}
public static void main(String[] args){
launch(args);
}
}
and this is the Exception.
Exception in thread "main" java.lang.RuntimeException: Error: class webviewtest.one.WebViewTestOne is not a subclass of javafx.application.Application
at javafx.application.Application.launch(Application.java:254)
at webviewtest.one.WebViewTestOne.main(WebViewTestOne.java:33)
Java Result: 1
So what is wrong? I mean since this is an Example from the official Site, why even there is an error? ( the error happens at the launch(args)
EDIT: Ok based on the Answer by rob I added the Extension that I missed from the example, Now it gives even much more exception after I tried to extend the code. below is the new Code and the Log for the exception.
package webviewtest.one;
import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.application.Platform;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.ListChangeListener.Change;
import javafx.concurrent.Worker.State;
import javafx.event.ActionEvent;
import javafx.event.Event;
import javafx.event.EventHandler;
import javafx.geometry.HPos;
import javafx.geometry.Pos;
import javafx.geometry.VPos;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.control.Hyperlink;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.Region;
import javafx.scene.paint.Color;
import javafx.scene.web.PopupFeatures;
import javafx.scene.web.WebEngine;
import javafx.scene.web.WebHistory;
import javafx.scene.web.WebHistory.Entry;
import javafx.scene.web.WebView;
import javafx.stage.Stage;
import netscape.javascript.JSObject;
public class WebViewTestOne extends Application{
private Scene scene;
#Override
public void start(Stage stage) {
// create scene
stage.setTitle("Web View");
scene = new Scene(new Browser(), 750, 500, Color.web("#666970"));
stage.setScene(scene);
// apply CSS style
scene.getStylesheets().add("webviewsample/BrowserToolbar.css");
// show stage
stage.show();
}
public static void main(String[] args) {
launch(args);
}
}
class Browser extends Region {
private HBox toolBar;
private static String[] imageFiles = new String[]{
"product.png",
"blog.png",
"documentation.png",
"partners.png",
"help.png"
};
private static String[] captions = new String[]{
"Products",
"Blogs",
"Documentation",
"Partners",
"Help"
};
private static String[] urls = new String[]{
"http://www.oracle.com/products/index.html",
"http://blogs.oracle.com/",
"http://docs.oracle.com/javase/index.html",
"http://www.oracle.com/partners/index.html",
// WebViewSample.class.getResource("help.html").toExternalForm()
};
final ImageView selectedImage = new ImageView();
final Hyperlink[] hpls = new Hyperlink[captions.length];
final Image[] images = new Image[imageFiles.length];
final WebView browser = new WebView();
final WebEngine webEngine = browser.getEngine();
final Button showPrevDoc = new Button("Toggle Previous Docs");
final WebView smallView = new WebView();
final ComboBox comboBox = new ComboBox();
private boolean needDocumentationButton = false;
public Browser() {
//apply the styles
getStyleClass().add("browser");
for (int i = 0; i < captions.length; i++) {
// create hyperlinks
Hyperlink hpl = hpls[i] = new Hyperlink(captions[i]);
Image image = images[i] =
new Image(getClass().getResourceAsStream(imageFiles[i]));
hpl.setGraphic(new ImageView(image));
final String url = urls[i];
final boolean addButton = (hpl.getText().equals("Documentation"));
// process event
hpl.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent e) {
needDocumentationButton = addButton;
webEngine.load(url);
}
});
}
comboBox.setPrefWidth(60);
// create the toolbar
toolBar = new HBox();
toolBar.setAlignment(Pos.CENTER);
toolBar.getStyleClass().add("browser-toolbar");
toolBar.getChildren().add(comboBox);
toolBar.getChildren().addAll(hpls);
toolBar.getChildren().add(createSpacer());
//set action for the button
showPrevDoc.setOnAction(new EventHandler() {
#Override
public void handle(Event t) {
webEngine.executeScript("toggleDisplay('PrevRel')");
}
});
smallView.setPrefSize(120, 80);
//handle popup windows
webEngine.setCreatePopupHandler((PopupFeatures config) -> {
smallView.setFontScale(0.8);
if (!toolBar.getChildren().contains(smallView)) {
toolBar.getChildren().add(smallView);
}
return smallView.getEngine();
});
//process history
final WebHistory history = webEngine.getHistory();
history.getEntries().addListener((Change<? extends Entry> c) -> {
c.next();
c.getRemoved().stream().forEach((e) -> {
comboBox.getItems().remove(e.getUrl());
});
c.getAddedSubList().stream().forEach((e) -> {
comboBox.getItems().add(e.getUrl());
});
});
//set the behavior for the history combobox
comboBox.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent ev) {
int offset =
comboBox.getSelectionModel().getSelectedIndex()
- history.getCurrentIndex();
history.go(offset);
}
});
// process page loading
webEngine.getLoadWorker().stateProperty().addListener(
new ChangeListener<State>() {
#Override
public void changed(ObservableValue<? extends State> ov,
State oldState, State newState) {
toolBar.getChildren().remove(showPrevDoc);
if (newState == State.SUCCEEDED) {
JSObject win =
(JSObject) webEngine.executeScript("window");
win.setMember("app", new JavaApp());
if (needDocumentationButton) {
toolBar.getChildren().add(showPrevDoc);
}
}
}
}
);
// load the home page
webEngine.load("http://www.oracle.com/products/index.html");
//add components
getChildren().add(toolBar);
getChildren().add(browser);
}
// JavaScript interface object
public class JavaApp {
public void exit() {
Platform.exit();
}
}
private Node createSpacer() {
Region spacer = new Region();
HBox.setHgrow(spacer, Priority.ALWAYS);
return spacer;
}
#Override
protected void layoutChildren() {
double w = getWidth();
double h = getHeight();
double tbHeight = toolBar.prefHeight(w);
layoutInArea(browser,0,0,w,h-tbHeight,0,HPos.CENTER,VPos.CENTER);
layoutInArea(toolBar,0,h-tbHeight,w,tbHeight,0,HPos.CENTER,VPos.CENTER);
}
#Override
protected double computePrefWidth(double height) {
return 750;
}
#Override
protected double computePrefHeight(double width) {
return 600;
}
}
and this is the Exception Log:
Exception in Application start method
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:363)
at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:303)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:875)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$147(LauncherImpl.java:157)
at com.sun.javafx.application.LauncherImpl$$Lambda$48/128893786.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException: Input stream must not be null
at javafx.scene.image.Image.validateInputStream(Image.java:1099)
at javafx.scene.image.Image.<init>(Image.java:684)
at webviewtest.one.Browser.<init>(WebViewTestOne.java:104)
at webviewtest.one.WebViewTestOne.start(WebViewTestOne.java:49)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$153(LauncherImpl.java:821)
at com.sun.javafx.application.LauncherImpl$$Lambda$51/1135703189.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$166(PlatformImpl.java:323)
at com.sun.javafx.application.PlatformImpl$$Lambda$45/1051754451.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$164(PlatformImpl.java:292)
at com.sun.javafx.application.PlatformImpl$$Lambda$47/135339377.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$165(PlatformImpl.java:291)
at com.sun.javafx.application.PlatformImpl$$Lambda$46/1775282465.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$141(WinApplication.java:102)
at com.sun.glass.ui.win.WinApplication$$Lambda$37/1109371569.run(Unknown Source)
... 1 more
Exception running application webviewtest.one.WebViewTestOne
Java Result: 1

You have to extend Application. I believe that is what the error means.
Here is an example from Java FX Site:
import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
public class MyApp extends Application
{
public void start(Stage stage)
{
Circle circ = new Circle(40, 40, 30);
Group root = new Group(circ);
Scene scene = new Scene(root, 400, 300);
stage.setTitle("My JavaFX Application");
stage.setScene(scene);
stage.show();
}
}

JavaFX - can't link controller with data array

I'm writing an music player and I can't link my Observable Array with TableView defined in controller. When project runned, I get NullPointerException on line under comment. I don't know what is making it happen and how find way around this problem.
Main.java
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.SplitPane;
import javafx.stage.Stage;
public class Main extends Application {
ObservableList<CModel> modelData = FXCollections.observableArrayList();
#Override
public void start(Stage primaryStage) {
try {
FXMLLoader loader = new FXMLLoader();
SplitPane root = FXMLLoader.load(getClass().getResource("Player.fxml"));
Scene scene = new Scene(root);
scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
primaryStage.setScene(scene);
PlayerController controller = loader.getController();
//this line gives exception
controller.setData(this);
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
public ObservableList<CModel> getPersonData() {
return modelData;
}
public static void main(String[] args) {
launch(args);
}
}
PlayerController.java
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Menu;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
public class PlayerController {
#FXML
private TableView<CModel> cTable;
#FXML
private TableColumn<CModel, String> artCol;
#FXML
private TableColumn<CModel, String> albCol;
#FXML
private TableColumn<CModel, String> trNameCol;
#FXML
private TableColumn<CModel, String> trNoCol;
#FXML
private TableColumn<CModel, String> durCol;
#FXML
private Menu addFile;
#FXML
private Menu addFolder;
#FXML
private Menu savePlayL;
#FXML
private Menu loadPlayL;
private Files files;
private Main main;
public PlayerController() {
}
#FXML
private void initialize() {
artCol.setCellValueFactory(
new PropertyValueFactory<CModel,String>("artistName")
);
albCol.setCellValueFactory(
new PropertyValueFactory<CModel,String>("albumName")
);
trNameCol.setCellValueFactory(
new PropertyValueFactory<CModel,String>("trackName")
);
trNoCol.setCellValueFactory(
new PropertyValueFactory<CModel,String>("trackDurationName")
);
durCol.setCellValueFactory(
new PropertyValueFactory<CModel,String>("trackNumberName")
);
}
#FXML
protected void handleAddFile(ActionEvent event) {
files = new Files();
files.openFile();
}
public void setData(Main mainApp) {
this.main = mainApp;
cTable.setItems(main.getPersonData());
}
}

You need to call loader.load() method of instantiated object, instead of using static method, before getting controller, take a look here for details.

There are few things to be considered here. In order to get the controller, you need to remember the following things :
Use the FXMLoader reference to load the FXML
Call the non-static load method. Inorder to do that pass a InputStream as a parameter.
Inside your Main.Java, you should have :
FXMLLoader loader = new FXMLLoader();
SplitPane root = (SplitPane)loader.load(getClass().getResource("Player.fxml").openStream());
If you don't want to use InputStream, you can also pass the resource in the constructor and call the non-staic load() method
FXMLLoader loader = new FXMLLoader(getClass().getResource("Player.fxml"));
SplitPane root = (SplitPane)loader.load();